I had this happen to me on Chrome (21.0.1180.79 m)...
But it didn't happen on Safari or on my ipad that I was testing on...

I also found that the display of the items, in my case year values on a date picker, were not displayed vertically centred in the div/row... as I scrolled through from 1900 to 2012, the gradually were displayed higher and higher up in the row until they were displaying where the value from the row above should have been...